The present invention relates to a circularly polarized zigzag antenna.
Zigzag antennas are known in the art, and are useful for broadcasting electromagnetic energy in the UHF frequency band. A conventional zigzag antenna generally takes the form of a solid or tubular conductor bent into a zigzag shape and disposed over a reflecting panel. Antennas of this type are disclosed in a number of United States patents including Woodward, U.S. Pat. No. 2,759,183; Fisk et al., U.S. Pat. Nos. 3,369,246 and 3,375,525; and Alford, U.S. Pat. No. 4,087,824. Although the antennas disclosed in these patents vary in certain structural aspects, they all share a common characteristic. In each case, the antenna will broadcast horizontally polarized electromagnetic energy.
The advantages of broadcasting or receiving circularly polarized signals, as opposed to horizontally polarized signals, has long been recognized. It has, for example, long been known that ghosting effects produced by reflections of the originally transmitted signal may be eliminated through use of circularly polarized signals.
A circularly polarized transmitting antenna for the UHF frequency band utilizing a zigzag antenna is disclosed in the IEEE Transactions on Broadcasting, Volume BC-24, No. 8, June, 1978, in an article by Andrew Alford. In this antenna, zigzag elements are again used for the conventional purpose of providing a horizontally polarized electromagnetic signal. Also used in conjunction with the zigzag elements, however, are other antenna elements whose purpose is to broadcast a vertically polarized signal in phase quadrature with the horizontal signal. The net effect is to provide a circularly polarized signal in the far field.